Coordinating installation and connection of a motor control center subunit having moveable line contacts

ABSTRACT

A system and method are provided for coordinating the installation and removal a motor control center subunit with the power connection and interruption thereof. A system of interlocks and indicators causes an operator to install a motor control center subunit into a motor control center, and connect supply and control power thereto, in a particular order. Embodiments of the invention may prevent actuation of line contacts of the bucket, and shield the line contacts, until the bucket is fully installed in the motor control center. Other embodiments also prevent circuit breaker closure until the line contacts are engaged with a bus of the motor control center.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation of and claims the benefit ofU.S. Ser. No. 11/694,494, filed on Mar. 30, 2007, which is acontinuation-in-part of and claims the benefit of U.S. Ser. No.11/625,088, filed on Jan. 19, 2007, now U.S. Pat. No. 7,688,572, whichclaims the benefit of U.S. provisional application Ser. No. 60/833,380,filed Jul. 26, 2006, the disclosures of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates generally to motor control systems, andmore particularly, to a motor control center subunit having an interlocksystem which governs the connection of motor control components tosupply power. In one embodiment, the system and method described hereincoordinate the connection of supply power to the motor controlcomponents to occur only after full installation of the motor controlcenter subunit into the motor control center.

A motor control center is a multi-compartment steel enclosure with a bussystem to distribute electrical power, on a common bus system, to aplurality of individual motor control units mountable within thecompartments. The individual motor control center subunits are commonlyreferred to as “buckets” and are typically constructed to be removable,pull-out units that have, or are installed behind, individual sealeddoors on the motor control center enclosure. These buckets may containvarious motor control and motor protection components such as motorcontrollers, starters, contactor assemblies, overload relays, circuitbreakers, motor circuit protectors, various disconnects, and similardevices for electric motors. The buckets connect to the supply powerlines of the motor control center and conduct supply power to the lineside of the motor control devices, for operation of motors. Motorcontrol centers are most often used in factories and industrialfacilities which utilize high power electrical motors, pumps, and otherloads.

Typically, when installing or removing motor control center buckets, thepower supply lines are connected. To remove such a bucket, a deadfrontdoor of the bucket or of the motor control center is opened and anoperator manually pulls on the bucket to separate the primarydisconnects, or “stabs,” from the bus system, thereby disconnecting thepower supply. Installation of a bucket is accomplished in a similarmanner, wherein the operator manually pushes the bucket into acompartment of the motor control center to engage the bucket stabs withthe bus system, thus connecting the system to supply power. The lineconnections or stabs may be difficult to maneuver manually when anoperator is supporting the entire bucket or when the stabs are notvisible.

Attempts have been made to improve upon the manual installation anddisconnection of motor control center buckets and supply powerconnections from live supply power lines, risers, and/or a vertical busof a motor control center. Other systems have employed pivotable handlesinside the buckets to pivot line connectors to and from supply lines.However, many of these systems require that the bucket or compartmentdoor be open to manipulate the handles and line stabs.

It would therefore be desirable to design a motor control center bucketassembly that overcomes the aforementioned drawbacks. Thus, it would bedesirable to provide for remote connection or disconnection of the linestabs of a bucket to the power supply lines or bus of a motor controlcenter from a distance. In the event of an arc or arc flash, any heatedgas, flame, and/or the arc itself should preferably be contained behindthe bucket compartment door or “deadfront.”

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a system and method for installing amotor control center subunit or bucket into a motor control center andelectrically connecting motor control components of the bucket to apower supply. The system and method utilize moveable line stabs toengage the power supply (such as a series of bus bars) after the buckethas been secured in the motor control center, in order to containpotential arc flashes. An arrangement of interlocks coordinates theconnection of supply power with installation and removal of the bucket.

Therefore, in accordance with one aspect of the present invention, amotor control center subunit is disclosed. The subunit includes ahousing configured to fit within a motor control center and an actuatingmechanism attached to the housing and constructed to move at least oneconductive contact to engage and disengage a supply power of the motorcontrol center. The subunit also includes an interlock system arrangedto coordinate installation of the subunit housing into the motor controlcenter with connection of the supply power to motor control componentsof the subunit housing.

In accordance with another aspect of the invention, a motor controlcenter is provided having a frame, a subunit, an actuating mechanism,and an interlock. The motor control center frame has at least onecompartment into which the motor control center's subunit is constructedto seat. The actuating mechanism is attached to the subunit to controlmovement of a plurality of conductive contacts. However, the interlockis configured to prevent actuation of the actuating mechanism until themotor control center subunit is seated in the compartment.

According to a further aspect of the invention, a method ofmanufacturing an interlock system for a motor control center isdisclosed. The method includes constructing a motor control centersubunit to seat within a motor control center. Engagement of a pluralityof movable contacts of the motor control center subunit with a supplybus of the motor control center is restricted, dependent upon a state ofat least one interlock.

Various other features and advantages of the present invention will bemade apparent from the following detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate one preferred embodiment presently contemplatedfor carrying out the invention.

In the drawings:

FIG. 1 is a partial perspective view of a number of motor control centersubunits installed in a motor control center.

FIG. 2 is a perspective view of a motor control center subunit of FIG.1, removed from the motor control center.

FIG. 3 is a top view of the motor control center subunit of FIG. 1showing a number of stabs in a refracted position.

FIG. 4 is top view of the motor control center subunit of FIG. 3 showingthe stabs in a test position.

FIG. 5 is a top view of the motor control center subunit of FIG. 4showing the stabs in an extended position.

FIG. 6 is a cross-sectional view of the motor control center subunit ofFIG. 3 taken along line 6-6 of FIG. 3.

FIG. 7 is a cross-sectional view of the motor control center subunit ofFIG. 5 taken along line 7-7 of FIG. 5.

FIG. 8 is a detailed view of a portion of the motor control centersubunit of FIG. 6 showing an arc shield, line contact, and supplyconductor thereof.

FIG. 9 is a detailed view of a portion of the motor control centersubunit of FIG. 7 showing a line contact and supply conductor thereof.

FIG. 10 is a plan view of a control handle of one embodiment of thepresent invention.

FIG. 11 is a side view of the control handle of FIG. 9.

FIG. 12 is a plan view showing the control handle of FIG. 9 rotatedninety degrees.

FIG. 13 is a side view of the control handle of FIG. 11.

FIG. 14 is a side view showing the control handle of FIG. 11 depressedinto a motor control center subunit.

FIG. 15 is a plan view showing the control handle of FIG. 11 rotatedninety degrees.

FIG. 16 is side view of the control handle of FIG. 14.

FIG. 17 is a bottom view of the motor control center subunit of FIG. 3.

FIG. 18 is a bottom view of the motor control center subunit of FIG. 5.

FIG. 19 is a rear perspective view of the motor control center subunitof FIG. 2.

FIG. 20 is a front view of the motor control center subunit of FIG. 3.

FIG. 21 is a front view of the motor control center subunit of FIG. 4.

FIG. 22 is a front view of the motor control center subunit of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description makes reference to supply power, supply powerlines, motor power, load power, line power, and the like. It isappreciated that such terms may refer to a variety of both common anduniquely conditioned voltage and current characteristics, including butnot limited to, three phase AC power, single phase AC power, DC power,multiple DC power lines, or any combination thereof. Such powercharacteristics will be generally referred to as being provided on abus, supply line, or riser of a motor control center. However, it isappreciated that the present invention may find applicability in otherpower connectivity configurations, adapted or apart from motor controlcenters. An example of supply power commonly used in motor controlcenters is 480V three-phase AC power distributed over three separatesupply bus bars. In addition, references to “motor control components”shall be understood to include the various types of devices and controlcomponents which may be housed in a motor control center bucket forconnection to the supply power. Such devices and components includecontactors, relays, motor controllers, disconnects, circuit protectivedevices, and the like.

Referring to FIG. 1, a partial perspective view of a motor controlcenter structure 10 is shown. As discussed above, motor control centersare generally formed of a frame 314 that may include compartments orenclosures for multiple control modules or buckets 11, 13, 14, 15, 16,17. Bucket 16 is shown fully installed into motor control centercompartment or enclosure 12 such that its front panel 18 is seatedsecurely against the periphery of enclosure 12 and flush with the frontpanel 20 of bucket 14. In this regard, bucket 16 includes a number oflatching mechanisms 22 on front panel 18 so that an operator may lockbucket 16 into place once installed. In some embodiments, front panel 18may be a deadfront door having a set of hinges 19 in order to permitaccess to motor control components within bucket 16 while bucket 16 isinstalled in enclosure 12 of motor control center 10. However, even whenclosed or sealed, front panel or door 18 still permits access to circuitbreaker assembly 28, stab indicator 24, shutter indicator 26, and linecontact actuator 31. Line contact actuator 31 is a mechanism forengaging line contacts (FIG. 2) with line power from the motor controlcenter 10. Thus, even when bucket 16 is fully installed in enclosure 12and latches 22 have been secured, an operator may still use disconnecthandle 30 and may open slide 32 to insert crank 34 to move one or moreline contacts (not shown) of the bucket 16. When slide 32 is moved asideto permit access to actuating mechanism 31, door 18 is prevented fromopening, thereby closing off access to components inside bucket 16.Additionally, a user may desire to padlock the slide 31 in the closedposition, to further regulate who may operate actuating mechanism 31 andwhen.

In other embodiments, a crank 300 for actuating an actuating assembly302 may include a flange 304 which abuts a front door 306 of a bucket 13when the crank 300 is connected to the actuating assembly 302 thereof.Because the flange 304 extends further than the actuating assembly 302and overlaps front door 306, flange 304 acts as an interlock to preventdoor 306 from opening when the crank 300 is connected for operation ofactuating assembly 302.

As an alternative to, or in combination with, using a hand crank, amotor drive 308 may be used to operate an actuating assembly 310 of abucket 17. Such a motor drive 308 may be connected permanently orremovably to actuating assembly 310. Preferably, motor drive 308 is a DCmotor remotely operable from distances of 10-50 ft, whether wirelesslyor with a wired controller. Motor drive 308 may be powered by a batteryor by an electrical connection with motor control center 10, such as viathe control power contact 44 shown in FIG. 2 or a similar plug orconnection. It is recognized, however, that many other types, sizes, andconfigurations of motor drive 308 are equivalently applicable. Forexample, it may be desirable to connect a motor drive 312 inside abucket, as shown with bucket 11. In addition, an interlock circuit maybe included (not shown) to only allow operation of the motor drive 308,312 when the bucket 11, 17 is installed in motor control center 10. Thismay be as simple as a contact switch that completes an input powercircuit or may include more sophisticated position sensors or latchsensors.

Referring now to FIG. 2, a perspective view of a motor control centerbucket 16 is shown. It is noted that bucket 16 may have a housing thatincludes a number of panels surrounding bucket 16 to fully or partiallyenclose the components thereof. As shown, bucket 16 includes a pair ofside panels 52 and a front panel 18, which support motor control devicesand internal bucket components. An upper panel and a rear panel havebeen removed to show the internal components of bucket 16. Front panel18 is configured to fit snugly and securely within a motor controlcenter such that a rim 38 of the front panel 18 seats against the innerperiphery (not shown) of a motor control center enclosure. For purposesof dust protection, rim 38 may optionally include a compressible orflexible seal, such as a rubber seal, or other gasket-type component.Once bucket 16 is inserted into a motor control center enclosure, latchmechanisms 22 may be turned with a key, a screwdriver, or by hand sothat latch arms 40 abut an inner surface of the outer periphery (notshown) of an enclosure to hold bucket 16 in place and/or prevent bucket16 from being removed. Similarly, an automatic retention latch 60 isshown in an engaged position. Upon advancement of line contacts or stabs46, 48, 50 automatic retention latch 60 is triggered to engage a frameor divider pan (FIG. 7) that segregates upper and lower compartments ofthe motor control center unit in which bucket 16 is installed.

When slide 32 of line contact actuator 31 is moved aside, an opening 36is exposed. Opening 36 preferably has a unique configuration to accept aspecialized crank 34 (as shown in FIG. 1). Additionally, when slide 32is moved aside as shown, slide 32 extends over a portion of front panel18. Thus, in embodiments in which front panel 18 is a hinged door,moving slide 32 to expose opening 36 will inhibit a user from openingfront panel 18. Accordingly, so long as an operator has a crank insertedinto opening 36 of actuator 31, the operator cannot open the door of thebucket 16.

Bucket 16 also includes a number of conductive contacts or stabs 44, 46,48, 50. Control power contact 44 is preferably fixedly attached to therear of bucket 16, whereas supply power stabs 46, 48, 50 are moveablewith respect to bucket 16. However, it is appreciated that control powercontact 44 may also be moveable in a similar manner to line power stabs46, 48, 50. Control power contact 44 is of a suitable construction toconduct a control power (typically a few volts) to motor controlcomponents (not shown) disposed within bucket 16. In embodiments wherecontrol power contact 44 is permanently positioned at the rear of bucket16, control power contact 44 will engage a control power supply line orbus upon installation of bucket 16 into a motor control center.

Supply power stabs 46, 48, 50, on the other hand, do not initiallyengage supply power lines or buses when bucket 16 is installed into amotor control center. Rather, stabs 46, 48, 50 are initially inretracted position 42, disposed inside bucket 16. One skilled in the artwill appreciate that a number of configurations of supply power stabs46, 48, 50 may be utilized. In the embodiment shown, stabs 46, 48, 50are shaped to grasp about a supply line, bus, or riser of the motorcontrol center 10 of FIG. 1.

The stab assembly 58, in addition to stabs 46, 48, 50, also includes astab bracket 59 to which the stabs 46, 48, 50 are attached. Stab bracket59 holds stabs 46, 48, 50 in an orientation for subsequent engagementwith the supply power lines or buses of motor control center 10 ofFIG. 1. It is recognized, however, that stab assembly 58 of FIG. 2 mayinclude any number of configurations, such as for independently moveablestabs, for other than three stabs, or for actuation by other than ashaft, as will be described below. A shutter or isolator assembly 54 isdisposed in the rear of bucket 16, between stab assembly 58 and theexterior of bucket 16. Isolator assembly 54 includes a number ofmoveable shutters 56 which operate to either expose or isolate the stabs46, 48, 50 from the power lines or buses of the motor control center 10of FIG. 1.

FIG. 3 depicts a top view of bucket 16, with all housing panels removedexcept for front panel or door 18. As shown, stab assembly 58 haspositioned stabs 46, 48, 50 in a retracted position 42 wherein the stabs46, 48, 50 are located inside bucket 16. Accordingly, shutters 56 ofshutter assembly 54 are closed, isolating the stabs 46, 48, 50 from thesupply power bus or line of a motor control center such as shown inFIG. 1. As shown in FIG. 3, each shutter 56 includes two separateshielding members 62 and 64, 66 and 68, 70 and 72. The shutter 56 forstab 46 includes a left shielding portion 62 and a right shieldingportion 64, each being angled toward stab 46. Likewise the shutters 56for stabs 48 and 50 include left shielding portions 66, 70 and rightshielding portions 68, 72 respectively, each being angled toward thecorresponding stab. However, the shutter 56 for stab 50 includes anadditional mechanical connection 74. That is, a shutter arm 74 isprovided to control a shutter indicating mechanism 76 which displays toan operator via front panel indicator 26 whether the shutters 56 areopen or closed, as will be described in further detail below. Similarly,a cam or bell crank 80 is attached via rod 78 to stab assembly 58 totranslate movement of the stab to a microswitch 82. Microswitch 82operates to turn on and off the supply of control power from controlpower contact 44 to motor control components, such as contactors oroverload relays (not shown), of bucket 16.

Referring now to FIG. 4, the bucket 16 is shown having the stab assembly58 in a test position 43. Stabs 46, 48, and 50 have been advanced to apoint or test position 43 at which they nearly touch or just touchshutters 56, but shutters 56 are still closed. Since shutters 56 areclosed, stabs 46, 48, 50 are isolated from supply power buses, thuspreventing arcs from occurring between stabs 46, 48, 50 and the buses.Being in the test position, stab bracket 59 is moved forward such thatactuating shaft or drive 84 is visible. Preferably, shaft 84 is a rotarydrive shaft and is connected to the socket of opening 36 shown in FIG. 2for operation via crank 34, shown in FIG. 1. Referring back to FIG. 4,during the advancement of stab assembly 58, automatic latch 60 has beentriggered to engage the enclosure of the motor control center into whichbucket 16 has been installed. Also due to the advancement of stabassembly 58, rod 78 is pulled by stab bracket 59 such that cam 80 hasrotated away from microswitch 82. Microswitch 82 is thus actuated topermit control voltage from the control power contact 44 to a motorcontrol component, such as a contactor or overload relay (not shown). Itis appreciated, however, that microswitch 82, cam 80 and rod 78 areoptional. In other words, embodiments of the present invention maysimply permit control voltage to pass through control power contact 44directly to motor control components immediately upon installation ofbucket 16 into a motor control center when contact 44 engages a controlpower bus.

FIG. 5 depicts another top view of the bucket 16 wherein the stabs 46,48, 50 are in an extended/engaged position 45. In operation, stabs 46,48, 50 are advanced or extended from the test position 43 of FIG. 4towards shutters 56 and impinge upon angled portions 62-72 of theshutters 56. As the stabs 46, 48, 50 are forced forward into and againstthe surfaces of shutters 56, the stabs 46, 48, 50 separate the leftangled portions 62, 66, 70 and right angled portions 64, 68, 72 of theshutters 56 to expose the stabs 46, 48, 50 to supply power buses 88, 90,92, respectively. Preferably, a biasing or closure force is provided tobias the right angled portions 64, 68 72 and the left angled portions62, 66, 70 towards one another, so that the shutters 56 automaticallyclose upon retraction of stabs 46, 48, 50. It is recognized thatnumerous other ways of opening and closing shutters 56 are possible andcontemplated. For example, rather than employing two shutter portionsfor each shutter, one shutter portion having one beveled surface couldbe slid aside by the advancement of the stabs. Or, the shutters could beconnected for manipulation by the turning of rotary shaft 84. Thus, theshutters 56 could comprise one or several sliding panels with or withoutbeveled surfaces. In other words, shutters 56 may be operated to openand close by the movement of the stabs, by the movement of the stabassembly, by the turning of the actuating shaft, by other actuatingcomponents, or by a manual control. Regardless, once the stabs 46, 48,50 have penetrated through shutters 56, the stabs 46, 48, 50 may beadvanced or extended to engage power supply bus bars 88, 90, 92.

Also shown in FIG. 5 is a second microswitch 94 connected to activateand deactivate circuit breaker 30. When stabs 46, 48, 50 reach the fullyengaged position 45 with bus bars 88, 90, 92, stab bracket 59 of stabassembly 58 actuates microswitch 94. When actuated, microswitch 94permits closure of circuit breaker 30, completing the circuit betweenbus bars 88, 90, 92 and the line side of motor control components (notshown) in bucket 16. Otherwise, microswitch 94 prevents closure ofcircuit breaker 30.

For removal of bucket 16, circuit breaker 30 is opened, disconnectingsupply power to the motor control devices (not shown) of bucket 16.Stabs 46, 48, 50 may then be retracted from bus bars 88, 90, 92 by areverse motion of rotary shaft 84. Once stabs 46, 48, 50 pass shutters56, the right and left portions 62-72 thereof will automatically closetogether to isolate the stabs from bus bars 88, 90, 92. Preferably, theshutter portions 62-72 and all or some of the housing panels, includingfront panel 18 and a rear panel (not shown), of bucket 16 are formed ofplastic or another insulating material. After stabs 46, 48, 50 have beenfully refracted, automatic latch 60 will release from engagement withthe motor control center, and an operator may then slide bucket 16 outof the motor control center.

Referring now to FIG. 6, a cross-sectional view of bucket 16 taken alongline 6-6 of FIG. 3 is shown. The left angled portion 66 of a shutter 56is shown isolating the central stab 48, since stab 48 is in theretracted position 42 of FIG. 3. In FIG. 6, it can be seen that stabassembly 58 holds stab 48 in position and engages rotary shaft 84, shownin section. Therefore, FIG. 6 illustrates the moving components used toactuate a stab 48. An operator may use a ratchet or crank (not shown)through opening 36 of slide 32 to turn rotary shaft or worm gear 84. Astab guide 96 includes a thread bearing 100 to transform the rotationalmotion of rotary shaft 84 into a translational motion of stab assembly58. Thus, rotary shaft 84 and stab guide 96 may generally be referred toas a racking-type actuating mechanism for extending and retracting thestabs 46, 48, 50, relative to bucket 16. As stab assembly 58 is rackedor otherwise advanced towards the extended or engaged position 45 shownin FIG. 5 (i.e. a motion to the left, as oriented in FIG. 6) stab 48will impinge upon shutters 66.

FIG. 6 also illustrates the operation of a number of interlocks whichcoordinate installation of the bucket 16 with connection of supplypower. That is, based upon the motion of the stab assembly 58, aretention latch 60 is triggered to retain bucket 16 in its installedposition inside the motor control center frame 314, followed by acircuit breaker interlock 316 being moved to permit an operator to closecircuit breaker handle 30 (FIG. 1). When stab assembly 58 is advanced, asloped lip 104 of stab assembly 58 will strike a bottom portion 106 ofautomatic retention latch 60. As sloped lip 104 follows the advancingmotion of the stab assembly 58, it will rotate retention latch 60 intoan upward position wherein bottom portion 106 rests on stab guide 96 andlatch 60 extends through a groove 98 of a divider pan 380 of the motorcontrol center frame (FIG. 1) to retain bucket 16 therein. Additionally,in the embodiment shown, a circuit breaker interlock 316 mechanicallyprevents an operator from closing a circuit breaker 28 (FIG. 1) whenstab assembly 58 is in the retracted position 42. This mechanicalembodiment of circuit breaker interlock 316 may be used in addition to,or as an alternative to, the microswitch embodiment shown in FIG. 5. Asshown in FIG. 6, circuit breaker interlock 316 has a downward-slopingend 320 and an upward-sloping end 318. The downward-sloping end 320 ofcircuit breaker interlock 316 acts as a stop, preventing plate 322 fromshifting. Plate 322 is interconnected with circuit breaker handle 30(FIG. 1), so that circuit breaker handle 30 cannot be turned unlessplate 322 shifts.

FIG. 7 is another cross-sectional view, showing the same portion ofbucket 16 as is shown in FIG. 6. However, FIG. 7 is a cross-sectiontaken along line 7-7 of FIG. 5, thus showing component locations whenthe stab assembly 58 is in the extended position 45. Stab assembly 58has been advanced by the turning of worm gear 84 such that stab 48 hasseparated and pushed past shutters 66. As the stab assembly 58 wasadvanced, sloped lip 104 of stab assembly 58 lifted bottom portion 106of retention latch 60, such that retention latch 60 now engages adivider pan 380 through opening 98. Divider pan 380 is connected to themotor control center frame (FIG. 1) to separate two bucket compartmentsthereof. Thereafter, as the stab assembly 58 reached its fully extendedposition 45, the stab guide 96 abutted the upward-sloped end 318 ofcircuit breaker interlock 316, drawing circuit breaker interlock 316away from plate 322. Thus, downward-sloped end 320 of circuit breakerinterlock 316 no longer blocks shifting of plate 322 when stab assembly58 is in the extended/engaged position 45. In other words, installationand power connection are coordinated in that a user cannot remove thebucket 16 from the motor control center once the automatic retentionlatch is triggered, and can only turn the circuit breaker handle 30(FIG. 1) when the stab assembly reaches its extended position 45.

FIG. 8 is an enlarged view of the stab 48 and shutter 66 area of thecross-sectional view of FIG. 6. Conductive stab 48 is coupled to aflexible conductor 130, such as a cable, via a coupling portion 132 ofstab assembly 58. Flexible conductor 130 is of a construction suitableto conduct supply power, via stab 48, to the line side of a motorcontrol component (not shown). As shown in FIG. 9, when stab 48 and stabassembly 58 are racked or otherwise advanced forward to an extendedposition 45, flexible conductor 130 flexes to maintain electricalconnectivity with stab 48 via coupler 132. Accordingly, the motion ofstab 48 relative to bucket 16 does not interfere with the connectivityof the stab 48 with a motor control component.

Referring now to FIGS. 10-16, an alternative stab actuating feature isshown. A manually drivable handle 116 may replace or be used incombination with the crank 34, the crank 300, the motor drive 308, orthe motor drive 312 of FIG. 1 and the racking mechanism of FIG. 6. Insuch embodiments, the rotary shaft or worm gear 84 depicted in previousembodiments may be replaced with a non-tapped shaft or rod directlyconnected to stab assembly 58. FIG. 10 shows such a handle 116 in alocked, starting position 118 that corresponds to the stabs disengagedposition 42 of FIG. 3. As shown in FIG. 11, handle 116 is separated andbiased from front panel 18 of a bucket by a spring 120 and extendsthrough stab actuating opening 36. By rotating handle 116 ninetydegrees, as shown in FIGS. 12 and 13, handle 116 may be unlocked 122. Insome embodiments, an interlock system may be included to preventunlocking of handle 116 until bucket 16 is fully installed into a motorcontrol center. Such an interlock may be incorporated into the shaft 84of handle 116. Once unlocked, handle 116 may be driven or depressedtowards front panel 16, compressing spring 120, as shown in FIG. 14. Thedepressed position 124 of handle 116 corresponds to the stabs engagedposition of FIG. 5. Handle 116 may then be rotated another ninetydegrees 126, as shown in FIGS. 15 and 16, to lock the handle in thestabs engaged position 124, against the force of spring 120. Fordisengagement of the stabs, handle 116 is rotated to unlockedorientation 122, pulled outward to the stab disengaged position 42 andturned ninety degrees to a locked position 118. In a general sense,therefore, embodiments of the present invention may include variousconfigurations of simplified, manual actuation of the stabs, similar tothat shown in FIGS. 10-16.

Referring now to FIG. 17, a bottom view of the bucket 16 of FIG. 3 isshown, wherein the stab assembly 58 and stabs 46, 48, 50 are in aretracted position 42. In retracted position 42, shutters 56 of shutterassembly 54 are closed, isolating or shielding stabs 46, 48, 50 insidebucket 16. Control power stab 44, on the other hand, is un-shielded andwill be connected to a control power once bucket 16 is installed into amotor control center. However, microswitch 82 is in an activated state,due to the pressure thereon by cam 80. When microswitch 82 is in theactivated state, as shown, microswitch 82 is interrupting control powerfrom contact 44. Thus, the motor control components (not shown) housedin bucket 16 cannot initially be operated. Cam 80 will be moved by rod78 via advancement of stab bracket 59, deactivating microswitch 82 andthereby permitting the flow of control power to motor control components(not shown) of the bucket 16. Cam 80 also acts to display a locationstatus of the stabs 46, 48, 50 to an operator. As will be discussedbelow, cam 80 has a number of colors printed thereon which are displayedthrough front door 18 of bucket 16 via stab indicator 24 (FIG. 1).

In the embodiment shown, circuit breaker interlock 316 includesmicroswitch 94, which gates the operation of circuit breaker 30. FIG. 17shows microswitch 94 in a deactivated state, in which button 334 thereofis not depressed. Arm 330 of microswitch 94 is positioned to abut aledge 332 of circuit breaker interlock 316 Thus, when circuit breakerinterlock 316 moves, due to the motion of stab assembly 58, the arm 330of microswitch 94 will pivot, depressing button 334. When button 334 isdepressed, microswitch 94 will be activated and will electrically enableoperation of circuit breaker 28 (FIG. 1).

Also shown in FIG. 17 is a shutter arm 336, having a sloped end 338. Asstab 46 is advanced, stab 46 will engage the sloped end 338 and slidepast shutter arm 336, thereby shifting shutter arm 336 to the left, asdepicted in FIG. 17. When shutter arm 336 is shifted, it will strike atab 340 of rod 76. As will be further described below, when tab 340 isstruck, rod 76 will rotate, changing the color showing on shutterindicator 26 through door 18 of bucket 16.

FIG. 18 is a bottom view of the bucket 16 of FIG. 5, illustrating thelocation of components thereof when the stab assembly 58 is in theextended/engaged position 45. When stab assembly 58 was advanced, rod 78caused cam 80 to rotate, releasing pressure on microswitch 82. Thus,microswitch 82 is shown in a deactivated state, permitting the flow ofcontrol power from control power contact 44 to motor control components(not shown) of bucket 16. Additionally, the advancement of stab assembly58 moved circuit breaker interlock 316 such that ledge 332 thereof drewarm 330 of microswitch 94 to an activated position. That is, arm 330 ofmicroswitch 94 is depressing button 334 to enable operation of circuitbreaker 30, now that stabs 46, 48, 50 are in the engaged position 45.

As discussed above, the advancement of stabs 46, 48, 50 to the extendedposition 45 separates a number of shutter portions, including shutterportion 62. In the embodiment shown in FIG. 18, the advancement of stab46 also caused a shift in shutter arm 336. That is, stab 46 impingedupon sloped end 338 of shutter arm 336 and drove shutter arm 336 to theleft, as depicted in FIG. 18, as stab 46 advanced. When shutter arm 336shifted due to the motion of stab 46, shutter arm 336 struck a tab 340(FIG. 17) of rod 76, rotating rod 76 and altering the color of shutterindicator 26.

Referring now to FIG. 19 a partial interior perspective view of a motorcontrol center bucket 16 is shown. For purposes of illustration, severalcomponents are not shown, including side panels, a top panel, a stabguide, and a circuit breaker assembly. Therefore, circuit breaker handle30 is visible through front door 18 of bucket 16. As shown, handle 30 isattached via a shaft 344 to a fin 346. Though not shown, a circuitbreaker assembly is also attached to be actuated by shaft 344.

Circuit breaker interlock 316 is shown in an alternate configuration,having an upward-sloping end 350 near door 18 and a pair of verticaltines 352 and one horizontal tine 354 at an opposite end. Vertical tines352 are engaged by a stab guide 96 (FIG. 7) when the stabs of bucket 16are advanced. Horizontal tine 354 engages a spring (not shown) to biasthe circuit breaker interlock 316 toward door 18 until the stabs ofbucket 16 are advanced. Until the circuit breaker interlock 316 is slidaway from door 18 by advancement of the stabs, upward-sloping end 350 ofcircuit breaker interlock 316 is inserted into an opening 356 ofinterlock plate 322. Because upward-sloping end 350 is inserted intoopening 356, interlock plate 322 is prevented from shiftingside-to-side, until circuit breaker interlock 316 is pulled away fromdoor 18 by the advancement of the stabs of bucket 16.

Interlock plate 322 has a projection 362 extending therefrom to fin 346of circuit breaker handle 30. Projection 362 is integrally formed with,or affixed to, plate 322, and is configured to move side-to-side withplate 322, when upward-sloping end 350 of circuit breaker interlock 316is not inserted in opening 356. Projection 362 has a pair of tines 348which extend outwardly therefrom, on either side of fin 346. Therefore,when plate 322 is prevented from moving, tines 348 prevent fin 346 fromrotating, thereby preventing an operator from turning circuit breakerhandle 30. In this manner, circuit breaker interlock 316 prevents a userfrom closing circuit breaker handle 30 until the stabs of bucket 16 arefully extended. It is understood that circuit breaker interlock 316,interlock plate 322, and associated components may have a number ofshapes, orientations, and configurations which allow for thefunctionality described herein.

When an operator closes circuit breaker handle 30, fin 346 impinges uponthe tines 348 of projection 362 in a counter-clockwise direction. Theforce of fin 346 on tines 348 causes projection 362 and interlock plate322 to shift to the left, as orientated in FIG. 19. When plate 322shifts left, it obscures opening 36 of actuating assembly 31 (FIG. 1),obstructing access to worm gear 84. So long as circuit breaker handle 30is closed, fin 346 will prevent plate 322 from moving back to the right,as shown in FIG. 19. In other words, fin 346 of circuit breaker handle30 effectively prevents a user from moving the stabs of bucket 16 whilethe circuit breaker is closed and supply power is conducting. Oncecircuit breaker handle 30 is opened again, fin 346 will not press ontines 348, plate 322 will be permitted to shift back to the positionshown in FIG. 19, and an operator will again have access to worm gear84. When the operator reverses worm gear 84 to withdraw the stabs,circuit breaker interlock 316 will be biased back toward plate 322,preventing plate 322 from sliding, and thus preventing circuit breakerhandle 30 from turning.

Also shown in FIG. 19 is cam 80 and rod 78. As discussed above withrespect to FIGS. 3 and 4, rod 78 is connected to translate movement ofthe stabs of bucket 16 to a rotational motion of cam 80. Cam 80 servestwo purposes: to activate and deactivate microswitch 82, as describedabove, and to control the stab location status shown on stab indicator24. Therefore, cam 80 has a number of colors printed on its edge.Visible in FIG. 19 are a red edge section 360 and a yellow edge section358. A green edge section (not shown) is currently being presented atstab indicator 24, to indicate the stabs refracted position 42 of FIG.3. Yellow edge section 358 will be presented at stab indicator 24 whenthe stabs have left the retracted position and are advanced towards thetest position 43 of FIG. 4. Red edge section 360 will be presented atstab indicator 24 when the stabs have reached the extended/engagedposition 45 of FIG. 5.

Similarly, rod 76 of shutter indicator 26 (FIG. 4) is connected to awheel 362, which presents a number of colors at shutter indicator 26, toindicate the status of the shutter assembly 54 (FIG. 3). That is, asdescribed with respect to FIG. 18, the movement of stab assembly 58causes a rotation in rod 76. As depicted in FIG. 19, rod 76 is affixedto wheel 364 such that a rotation of rod 76 causes wheel 364 to turn.

Referring now to FIGS. 20-22, the status indicating features of stabindicator 24 and shutter indicator 26 are shown. That is, FIGS. 20, 21,and 22 are a front view of the bucket 16 shown in FIGS. 3, 4, and 5,respectively. With respect to FIG. 20, a user has moved slide 32 ofactuating assembly 31 to the right, exposing opening 36. In alternativeembodiments, a user may need to unlock a cover or padlock (not shown)which restrict movement of or access to the slide 32. As shown, slide 32overlaps door 18, preventing a user from opening door 18 while opening36 is exposed. Shutter indicator 26 is displaying a green “shuttersclosed” status 368, since the shutters 56 are closed due to the stabsretracted position 42 of FIG. 3. Therefore, FIG. 20 also shows stabindicator 24 displaying a green “stabs refracted” status, correspondingto the stabs retracted position 42 of FIG. 3. FIG. 21 also shows thegreen “shutters closed” status 368 on shutter indicator 24, but shows ayellow “test position” status on the stab indicator 24, corresponding tothe test position 43 of FIG. 4.

FIG. 22 shows a front view of bucket 16 when the stabs are in theextended/engaged position 45 of FIG. 5. Therefore, shutter indicator 26now displays a red “shutters open” status 370, since the stabs 46, 48,50 have separated the shutters 56 (FIG. 5), and the stab indicator 24 ofFIG. 22 shows a red “stabs engaged” status 360. Circuit breaker handle30 has been turned, closing the circuit breaker 31 and permitting theflow of supply power to motor control components inside bucket 16. Asdescribed above with respect to FIG. 19, turning circuit breaker handle30 when the stabs are engaged causes interlock plate 322 to be shiftedby movement of circuit breaker fin 346. Accordingly, FIG. 22 illustratesthat actuating assembly opening 36 is now obscured by interlock plate322. It is understood that further measures, such as padlocking a coverover actuating mechanism 31 and slide 32, may also be made to furtherrestrict access to the actuating mechanism 31 when the bucket 16 isconnected to supply power.

Thus, an interlock system has been disclosed, in a number ofembodiments, which coordinates the installation and power connections ofa motor control center subunit or bucket. When a user slides the bucketcompletely into the enclosure of a motor control center, the linecontacts or stabs of the bucket are shielded from the bus bars. Once thebucket is inserted into the enclosure, the front door of the bucket mustbe closed and the circuit breaker must be off/open in order for theoperator to have access to the stab actuating mechanism. Additionally, auser may have to unlock a padlock and latch to gain access to the slideand/or actuating mechanism. Once the actuating mechanism opening isexposed, a crank (or motor drive) may be connected thereto. The stabindicator will show a green “stabs-disengaged” status, and the shutterindicator will show a green “shutters-closed” status. As the stabs areinitially advanced, an automatic retention latch is triggered to engagethe frame of the motor control center and prevent removal of the buckettherefrom. Also, a micro-switch is activated by the initial advancementof the stabs, turning on control power for the motor control componentsinside the bucket. When the line stabs reach the back of the bucket, buthave not moved past the shielding shutters, the bucket is in the “test”position. The stab indicator will show a yellow “test” status, and theshutter indicator will still show a green “shutters-closed” status. Whenthe stabs are advanced further, they will open the shutters, causing theshutter indicator to show a red “shutters-open” status. When theshutters reach and engage the bus bars, the stab indicator will show ared “stabs-engaged” status and the circuit breaker interlock will betripped. At this point, the circuit breaker will be permitted to closeonce the user removes the crank or motor from the actuating mechanism.When a user closes the circuit breaker, access to the actuatingmechanism will be obscured by a circuit breaker interlock plate. Thecircuit breaker handle and/or the actuating mechanism slide can bepadlocked in place at this point to maintain the engaged, operatingstate now achieved. Moreover, it is understood that the interlock systemthus disclosed also coordinates the power disconnection and removal ofthe bucket from the motor control center, by reverse operation of theaforementioned interlocks and indicators.

Accordingly, one embodiment of the present invention includes a motorcontrol center subunit having a subunit housing, an actuating mechanism,and an interlock system. The subunit housing is configured to fit withina motor control center. The actuating mechanism is attached to thesubunit housing and is constructed to move at least one conductivecontact to engage and disengage a supply power of the motor controlcenter. The interlock system is arranged to coordinate installation ofthe subunit housing into the motor control center with connection of thesupply power to motor control components of the subunit housing.

In accordance with another embodiment of present invention, a motorcontrol center includes a frame having at least one compartment and asubunit constructed to seat in the at least one compartment of the motorcontrol center frame. An actuating mechanism is attached to the motorcontrol center subunit to control movement of a plurality of conductivecontacts and an interlock is configured to prevent actuation of theactuating mechanism until the motor control center subunit is seated inat least one compartment.

In another embodiment of the present invention, a method ofmanufacturing an interlock system for a motor control center isprovided. The method includes constructing a motor control centersubunit to seat within a motor control center and restricting engagementof a plurality of movable contacts of the subunit with a supply bus ofthe motor control center dependent upon a state of at least oneinterlock.

The present invention has been described in terms of the preferredembodiment, and it is recognized that equivalents, alternatives, andmodifications, aside from those expressly stated, are possible andwithin the scope of the appending claims.

What is claimed is:
 1. A control module for a motor control centercomprising: a housing constructed to be received within a frame of themotor control center; a stab assembly comprising: a stab guide; and atleast one line contact coupled to the stab guide, the at least one linecontact moveable between a retracted position and an extended position;and a rotatable latch disposed proximate a top surface of the stabguide, wherein the rotatable latch comprises a base plate and a pair ofside plates extending upward from the base plate.
 2. The control moduleof claim 1 wherein the rotatable latch is moveable between a firstposition and a second position; wherein the rotatable latch engages theframe of the motor control center in the first position; and wherein therotatable latch is disengaged with the frame of the motor control centerin the second position.
 3. The control module of claim 1 furthercomprising a drive mechanism coupled to the stab guide.
 4. The controlmodule of claim 3 wherein the drive mechanism comprises a rotary drive.5. The control module of claim 4 further comprising: a threaded bearingcoupled to the stab guide and threadedly engaged with the rotary drive;and a front panel coupled to the housing, wherein a first end of therotary drive is accessible through an opening in the front panel.
 6. Thecontrol module of claim 1 wherein the rotatable latch translates betweena first end of the top surface of the stab guide and a second end of thetop surface of the stab guide as the at least one line contact is movedbetween the retracted position and the extended position.
 7. A motorcontrol center comprising: a motor control center frame having aplurality of control module openings, each control module opening havingtherein at least one bus bar connected to line power and a plurality ofinternal walls defining a control module cavity, and wherein at leastone internal wall has a retention latch opening therein; and a pluralityof motor control buckets, each motor control bucket comprising: a stabassembly having at least one conductive contact engagable with the atleast one bus bar in the control module cavity; and a racking mechanismmounted to the motor control bucket and connected to the stab assemblywithin the motor control bucket to advance and retract the at least oneconductive contact with regard to the at least one bus bar of the motorcontrol center frame; and a retention latch connected to the rackingmechanism and positioned adjacent an outer surface of the motor controlbucket and the retention latch opening of the motor control centerframe, the retention latch having a retracted position when the rackingmechanism is retracted allowing insertion of the motor control bucketinto the control module cavity of the motor control center frame, and anengaged position wherein at least a portion of the retention latchextends beyond an outer periphery of the motor control bucket when theracking mechanism is advanced.
 8. The motor control center of claim 7wherein the retention latch engages an outer surface edge of the motorcontrol center frame to prevent insertion of the motor control bucketinto the control module cavity of the motor control center frame when inan engaged position.
 9. The motor control center of claim 7 wherein andretention latch prevents removal of the motor control bucket from thecontrol module cavity of the motor control center frame when in theengaged position; and wherein the portion of the retention latchextending beyond the outer periphery of the motor control bucket isengaged into the retention latch opening of the motor control centerframe.
 10. The control module of claim 1 wherein the rotatable latchextends outside the housing through an opening in a top panel of thehousing.
 11. A control module for a motor control center comprising: ahousing constructed to be received within a frame of the motor controlcenter; a stab assembly comprising: a stab guide; and at least one linecontact coupled to the stab guide, the at least one line contactmoveable between a retracted position and an extended position; and arotatable latch disposed proximate a top surface of the stab guide,wherein the rotatable latch comprises a first surface that engages theframe of the motor control center and a second surface that translatesacross the top surface of the stab guide.
 12. The control module ofclaim 11 wherein the rotatable latch extends outside the housing throughan opening in a top panel of the housing.
 13. The control module ofclaim 11 wherein the rotatable latch comprises a base plate and a pairof side plates extending upward from the base plate.
 14. The controlmodule of claim 11 further comprising a drive mechanism coupled to thestab guide.
 15. A control module for a motor control center comprising:a housing constructed to be received within a frame of the motor controlcenter; a stab assembly comprising: a stab guide; and at least one linecontact coupled to the stab guide, the at least one line contactmoveable between a retracted position and an extended position; and arotatable latch disposed proximate a top surface of the stab guide,wherein the rotatable latch translates between a first end of the topsurface of the stab guide and a second end of the top surface of thestab guide as the at least one line contact is moved between theretracted position and the extended position.
 16. The control module ofclaim 15 wherein the rotatable latch extends outside the housing throughan opening in a top panel of the housing.
 17. The control module ofclaim 15 wherein the rotatable latch comprises a base plate and a pairof side plates extending upward from the base plate.
 18. The controlmodule of claim 15 wherein the rotatable latch comprises a first surfacethat engages the frame of the motor control center and a second surfacethat translates across the top surface of the stab guide.
 19. Thecontrol module of claim 15 wherein the first end of the top surface ofthe stab guide comprises a downward facing surface.
 20. The controlmodule of claim 15 further comprising a drive mechanism coupled to thestab guide.